Mark Briffa's favourites

Dr Mark Briffa is an Associate Professor of Animal Behaviour at the School of Marine Science and Engineering, Plymouth University, UK. His main research focuses on the evolution of agonistic signals and other aggressive behaviours. He joined Biology Letters as a Handling Editor in 2014.

"Due to its short paper format, Biology Letters tends to publish papers that test a clearly formulated idea in a straightforward way. This does not mean of course that these studies are easy to do or that the hypotheses tested are obvious or trivial. On the contrary, formulation of a clear question is an essential step, especially so in animal behaviour experiments. Often we are trying to tease out exactly what might be going on in study subjects that are abundantly open to myriad sources of influence. Nailing down a coherent hypothesis under these conditions is far from easy, but my four choices below demonstrate how it can be done. Chosen to reflect my own interests in animal communication and contest behaviour, each utilises a well thought out experiment to address a fundamental and longstanding question in animal behaviour. As well as attracting the interest of a broad range of researchers, these papers are also ones that will grab the attention of that other group of readers that scientific journals should attract – our current students who contain the next generation of researchers."

What factors contribute to an ownership advantage?

"Some of the best insights in animal behaviour emerge from a body of studies performed on a system that the authors are intimately acquainted with. Semi-terrestrial fiddler crabs are famous due to the conspicuously enlarged claw of males. In a series of papers Backwell and Jennions and their collaborators have used ingenuous experiments to try and get to the bottom of exactly how males use this sexually selected trait. As well as waving it to attract females, they also use the claw to fight off other males who want to take over their burrow and territory. This particular study by Fayed et al. addresses a real puzzle in animal contests: Why are resource owners often more likely to win than would-be usurpers? In this case owners were not inherently better at fighting and only had marginally better knowledge about the value of the territory than floaters. However, by carefully blocking the burrow entrances at the onset of fights, the authors demonstrated that fighting from a position of defence was easier than attacking. It seems bracing against the burrow entrance gives owners a mechanical advantage over attackers. Having spent some time watching fiddler crabs on field courses I know that they can be difficult animals to work with. They live in a punishing environment on mud flats and they are very sensitive to disturbance; one false move and off they scuttle back into their burrows. Even so, students are always fascinated by their encounters with Uca and papers like this one are responsible for inspiring many a student to study animal behaviour. I like this study not only because of the important result but also because it’s a great example of what can be achieved when a clearly conceived hypothesis is combined with a lot of time spent carefully observing animals."

Abstract
In most taxa, owners win fights when defending a territory against intruders. We calculated effect sizes for four factors that potentially contribute to an ‘owner advantage’. We studied male fiddler crabs Uca mjoebergi, where owners won 92% of natural fights. Owners were not more successful because they were inherently better fighters (r=0.02). There was a small effect (r=0.18) of the owner's knowledge of territory quality (food availability) and a medium effect (r=0.29) of his having established relations with neighbours (duration of active tenure), but neither was statistically significant. There was, however, a significant effect due to the mechanical advantage the owner gained through access to the burrow during fights (r=0.48, p<0.005).

Male dance moves that catch a woman's eye

"Signals that advertise individual quality have been studied from a variety of perspectives. Aspects including magnitude, repetition rate, repertoire size and complexity are frequently studied but one facet that has probably been understudied in skill. Individuals might differ not only in performance capacity but in their competence to perform the signal well and receivers might therefore be able to glean some information from variation in skill. This study by Neave et al. addresses this question in humans, using some cutting edge video and computer technology. Using a motion capture system they filmed 30 men dancing to a standardised drum beat for 30s each. No instruction was given about how the dance should be performed. These films were used to animate computer generated avatars, which were then observed by females who rated the dances for quality. It turns out that a few very specific aspects* of the dance moves determine the overall rating. Although it is not yet clear what components of male quality might be advertised by motor skill, studies like this one point to new ways of analysing animal signals. Similar approaches have been used for example to investigate displays in other primates such as golden collared manakins. It will be very interesting to see whether motor skill becomes an element of studies looking at signals across diverse animals and in different contexts.

*Neck, trunk and right knee; please read the paper for full details. Perhaps those end of conference parties will never be the same again."

Abstract
Male movements serve as courtship signals in many animal species, and may honestly reflect the genotypic and/or phenotypic quality of the individual. Attractive human dance moves, particularly those of males, have been reported to show associations with measures of physical strength, prenatal androgenization and symmetry. Here we use advanced three-dimensional motion-capture technology to identify possible biomechanical differences between women's perceptions of ‘good’ and ‘bad’ male dancers. Nineteen males were recorded using the ‘Vicon’ motion-capture system while dancing to a basic rhythm; controlled stimuli in the form of avatars were then created in the form of 15 s video clips, and rated by 39 females for dance quality. Initial analyses showed that 11 movement variables were significantly positively correlated with perceived dance quality. Linear regression subsequently revealed that three movement measures were key predictors of dance quality; these were variability and amplitude of movements of the neck and trunk, and speed of movements of the right knee. In summary, we have identified specific movements within men's dance that influence women's perceptions of dancing ability. We suggest that such movements may form honest signals of male quality in terms of health, vigour or strength, though this remains to be confirmed.

"A persistent question about animal contests is what factors determine the course and outcome of fights. The fighting abilities of the opponents will have a major influence but so too should the value of the contested resource. We would expect rivals to be more motivated to fight over a high value item than over a low value one. There are, however, two ways of looking at resource value. A resource unit will have properties that can be quantified in absolute terms but it is also true that the resource may have a subjective value specific to each opponent. Quantifying the difference in how each opponent values the resource, let alone manipulating this, can be tricky. But this is precisely what Stockermans and Hardy were able to do in this study of fighting in parasitoid wasps. Females lay their eggs in moth larvae and the value increases objectively with host size and subjectively with the female’s age. Therefore, the two components can be manipulated independently in staged fights. This study shows very clearly that the objective and subjective components have an additive effect on aggressiveness and that, of the two, subjective resource value has the stronger effect. This finding has the potential to inform future models of fighting behavior. Perhaps more importantly, this work demonstrates how the biology of a particular study species can be exploited to tease apart these different drivers of behaviour."

Abstract
Two major categories of factors are predicted to influence behaviour in dyadic contests; differences in the abilities of the contestants to acquire and retain resources (resource holding potential), and the value of the contested resource (resource value, RV; which comprises objective and subjective components). Recent studies indicate that subjective components affect contest behaviour in several animal taxa but few have simultaneously investigated objective RV components. We find that both an objective (host size) and a subjective (contestant age) component of RV affect contest intensity in the parasitoid wasp Goniozus legneri. These additively influence aggressiveness, with a larger effect from the subjective component than the objective component. The greater influence of subjective RV adds weight to the recent surge of recognition of this RV component's importance in contest behaviour.

Lateralization of lateral displays in convict cichlids

"Some of the clearest insights into functional aspects of behaviour come after learning more about the mechanisms involved. This study by Arnott et al. shows why this can also be so important from a methodological point of view. In many vertebrates contests involve lateral displays where the opponents expose their flanks to one-another. In the case of convict cichlid fish, the rivals align head to tail during this display, rather than head to head as in other species. In a head to tail arrangement injuries are likely to be less common than in head to head fights. A possible causal factor for this orientation is that the behaviour is heavily lateralised – most the information gathered during the encounter is processed in one side of the brain. In this study it was found that in most encounters the focal fish displayed its right side to the rival and that display bouts in this orientation lasted longer than those where the left flank was displayed. This indicates that the display is indeed lateralised, favouring information gathering with the right eye. This study reveals a mechanism that could allow for contests where the risk of mutual injury is reduced and hence there is a degree of cooperation between the rivals. From a methods point of view, many studies of aggression in fish rely on mirror tests, where the subject displays to its own reflection. In the light of this study we now have to consider the limits of this approach, since the subject will always be displaying to its opponent in head to head mode."

Abstract
We examine lateralization of lateral displays in convict cichlids, Amatitlania nigrofasciata, and show a population level preference for showing the right side. This enables contesting pairs of fish to align in a head-to-tail posture, facilitating other activities. We found individuals spent a shorter mean time in each left compared with each right lateral display. This lateralization could lead to contesting pairs using a convention to align in a predictable head-to-tail arrangement to facilitate the assessment of fighting ability. It has major implications for the common use of mirror images to study fish aggression, because the ‘opponent’ would never cooperate and would consistently show the incorrect side when the real fish shows the correct side. With the mirror, the ‘normal’ head-to-tail orientation cannot be achieved.